1. Technical Field
The present invention relates to a sensor.
2. Related Art
Infrared sensors or terahertz sensors are broadly classified, in terms of the detection principle, into quantum types and thermal types. Of these types of sensors, thermal-type sensors need not be cooled in order to prevent noise. For this reason, thermal-type sensors have attracted much attention. For example, the usage of infrared sensors of the pyroelectric type, which is one of the thermal types, as human sensors and so forth has become widespread, and such sensors can acquire information on the presence of a human body and the temperature of the human body in a noncontact fashion by detecting infrared rays having a wavelength of about 10 μm that are radiated from the human body. Such a pyroelectric-type infrared sensor includes a thermoelectric transducer (hereinafter sometimes referred to as a pyroelectric element).
A pyroelectric element has the property of absorbing thermal energy of infrared rays to cause a temperature change and inducing electric charges in accordance with the temperature change. Lead zirconate titanate (hereinafter abbreviated as PZT) expressed by a composition formula of Pb(Zr, Ti)O3, for example, with which a relatively large pyroelectric coefficient is obtained is known as a material of a pyroelectric element.
However, in order to improve sensitivity, responsivity, and so forth, the size of one pixel of a pyroelectric material in an infrared sensor has recently been made very small. This makes it difficult to produce a sensor from a bulk material. To address this issue, a pyroelectric sensor using spin-coated PZT as a pyroelectric material has been proposed (see JP-T-2003-530538).
Unfortunately, when PZT in the form of a thin film as described in JP-T-2003-530538 is used, a problem arises in that it is difficult to achieve good infrared sensor sensitivity.